Plot method for objects of class "PerFit".

1 2 3 4 5 6 7 8 9 10 11 12 | ```
## S3 method for class 'PerFit'
plot(x, cutoff.obj=NULL,
ModelFit="NonParametric", Nreps=1000,
IP=x$IP, IRT.PModel=x$IRT.PModel, Ability=x$Ability,
Ability.PModel=x$Ability.PModel, mu=0, sigma=1,
Blvl = 0.05, Breps = 1000, CIlvl = 0.95,
UDlvl = NA,
Type="Density", Both.scale=TRUE, Cutoff=TRUE, Cutoff.int=TRUE,
Flagged.ticks = TRUE,
Xlabel=NA, Xcex=1.5, title=NA, Tcex=1.5,
col.area="lightpink", col.hist="lightblue", col.int="darkgreen",
col.ticks="red", ...)
``` |

`x` |
Object of class "PerFit". |

`cutoff.obj` |
Object of class "PerFit.cutoff". |

`ModelFit` |
Method required to compute model-fitting item score patterns. The options available are |

`Nreps` |
Number of model-fitting item score patterns generated. Default is 1000. |

`IP` |
Matrix with previously estimated item parameters. Default is |

`IRT.PModel` |
Parametric IRT model (required if |

`Ability` |
Matrix with previously estimated item parameters. Default is |

`Ability.PModel` |
Method to use in order to estimate the latent ability parameters (required if |

`mu` |
Mean of the apriori distribution. Only used when |

`sigma` |
Standard deviation of the apriori distribution. Only used when |

`Blvl` |
Significance level for bootstrap distribution (value between 0 and 1). Default is 0.05. |

`Breps` |
Number of bootstrap resamples. Default is 1000. |

`CIlvl` |
Level of bootstrap percentile confidence interval for the cutoff statistic. |

`UDlvl` |
User-defined cutoff level. |

`Type` |
Type of plot: |

`Both.scale` |
Logical: Should the y-axis be adjusted so that both the histogram and the density graphics are completely visible? Default is |

`Cutoff` |
Logical: Should the estimated cutoff be added to the plot? Default is |

`Cutoff.int` |
Logical: Should an approximated (1-Blvl)% bootstrap confidence interval be added to the plot? Default is |

`Flagged.ticks` |
Logical: Should ticks representing the flagged respondents be added to the plot? Default is |

`Xlabel` |
Label of x-axis, otherwise a default label is shown. |

`Xcex` |
Font size of the label of x-axis. |

`title` |
Title of the plot, otherwise a default title is shown. |

`Tcex` |
Font size of the title of the plot. |

`col.area` |
Color of "flagging region". |

`col.hist` |
Color of histogram. |

`col.int` |
Color of bootstrap confidence interval. |

`col.ticks` |
Color of the ticks marking the flagged respondents. |

`...` |
Extra graphical parameters to be passed to |

This function plots the empirical distribution of the scores of the person-fit statistic specified by the "PerFit" class object `x`

. A histogram, density, or a combination of both displays is possible.

The cutoff score may be provided by means of the `cutoff.obj`

object, otherwise it is internally computed (for which the function parameters `ModelFit`

through `CIlvl`

are required; see `cutoff`

for more details). The value of the cutoff is superimposed to the plot when `Cutoff=TRUE`

. In this case, the adequate "flagging region" is colored, thus indicating the range of values for which the person-fit statistic flags respondents as potentially displaying aberrant behavior. The option `Both.scale`

was introduced to help to better tune the scale of the y-axis. Furthermore, the percentile confidence interval for the cutoff value (with confidence level defined by the `cutoff.obj`

) is displayed in the x-axis, and ticks marking the flagged respondents are display on the top of the plot.

Jorge N. Tendeiro j.n.tendeiro@rug.nl

1 2 3 4 5 6 7 8 9 | ```
# Load the inadequacy scale data (dichotomous item scores):
data(InadequacyData)
# Compute the ZU3 scores:
ZU3.out <- ZU3(InadequacyData)
# Plot the sampling distribution of the ZU3 scores, with cutoff value based on a nominal 5% level,
# and 90% confidence interval:
plot(ZU3.out, Type="Both", Blvl=.05, CIlvl = 0.90)
``` |

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